electrical engineering Mcqs
1. economics of power generation2. analog electronics3. solid state switching circuits4. parallel circuits5. switchgear and protection6. op amp circuits7. transistor audio power amplifiers8. electrostatics9. heating and welding10. multi stage transistor amplifiers11. passive filters12. network theorems13. regulated d c power supply14. a c fundamentals circuits and circuit theory15. electromagnetic induction16. power electronics17. magnetism and electromagnetism18. transformers19. modulation and demodulation20. d c generators21. semiconductor theory22. single phase induction motors23. semiconductor diode24. hybrid parameters25. digital electronics26. oscillators27. earthing or grounding28. single stage transistor amplifiers29. d c motors30. transistor biasing31. amplifiers with negative feedback32. basic electrical33. electronic instruments34. synchronous motors35. field effect transistors fet36. magnetic circuit37. control systems38. industrial drives39. power generation40. series parallel circuits41. transistor tuned amplifiers42. electrical engineering materials43. rectifiers and converters44. integrated circuits45. scr silicon controlled rectifiers46. cables47. polyphase induction motors48. measurement and instrumentation49. transistors50. electrical machine design51. electrolysis and storage of batteries52. electric traction53. transmission and distribution
5051. Helical coils can be used on___________________?
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A. low voltage side of high kVA transformers

B. high voltage side of high kVA rating transformers

C. high frequency transformers

D. high voltage side of small capacity transformers

5052. In the transformer following winding has got more cross-sectional area______________?
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A. High voltage winding

B. Primary winding

C. Secondary winding

D. Low voltage winding
5053. If the percentage impedances of the two transformers working in parallel are different, then______________________?
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A. transformers will be overheated

B. power factors of both the transformers will be same

C. parallel operation will be not possible

D. parallel operation will still be possible, but the power factors at which the two transformers operate will be different from the power factor of the common load
5054. A transformer transforms__________________?
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A. power

B. current

C. voltage

D. frequency

5055. An ideal transformer will have maximum efficiency at a load such that?
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A. copper loss iron loss

B. copper loss = iron loss

C. none of the above

5056. In a transformer the resistance between its primary and secondary is____________?
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A. 1 ohm

B. 1000 ohms

C. zero

D. infinite
5057. N atural air coo ling is generally restricted for transformers up to__________?
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A. 15 MVA

B. 1.5 MVA

C. 5 MVA

D. 50 MVA

5058. An open-circuit test on a transformer is conducted primarily to measure______________?
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A. total loss

B. none of the above

C. core loss

D. copper loss

E. efficiency

F. insulation resistance

5059. Efficiency of a power transformer is of the order of________________?
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A. 100 per cent

B. 25 per cent

C. 98 per cent

D. 50 per cent

5060. Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds?
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A. 80C

B. 50C

C. 150C

D. 100C

5061. The noise produced by a transformer is termed as_______________________?
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A. hum

B. zoom

C. ringing

D. buzz

5062. Which of the following loss in a transformer is zero even at full load ____________?
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A. Eddy current loss

B. Friction loss

C. Core loss

D. Hysteresis loss

5063. An ideal transformer is one which has_____________?
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A. none of the above

B. interleaved primary and secondary windings

C. no losses and magnetic leakage

D. a common core for its primary and secondary windings

E. core of stainless steel and winding of pure copper metal

5064. A transformer oil must be free from________________?
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A. gases

B. moisture

C. odour

D. sludge

5065. In a transformer the tappings are generally provided on_____________?
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A. secondary side

B. primary side

C. high voltage side

D. low voltage side

5066. Material used for construction of transformer core is usually___________________?
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A. copper

B. aluminium

C. silicon steel

D. wood

5067. The maximum efficiency of a distribution transformer is____________?
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A. at no load

B. at full load

C. at 80% full load

D. at 50% full load
5068. A shell-type transformer has_________?
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A. negligibly hysteresis losses

B. none of the above

C. high eddy current losses

D. reduced magnetic leakage
5069. The size of a transformer core will depend on__________?
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A. frequency

B. flux density of the core material

C. A. and B. both

D. area of the core

5070. For the parallel operation of single phase transformers it is necessary that they should have___________?
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A. same efficiency

B. same polarity

C. same kVA rating

D. same number of turns on the secondary side.

5071. Primary winding of a transformer________________?
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A. is always a low voltage winding

B. could either be a low voltage or high voltage winding

C. is always a high voltage winding

D. none of the above

5072. The maximum load that a power transformer can carry is limited by its________________?
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A. voltage ratio

B. dielectric strength of oil

C. copper loss

D. temperature rise

5073. The secondary of a current transformer is always short-circuited under operating conditions because it____________________?
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A. protects the primary circuit

B. is safe to human beings

C. none of the above

D. avoids core saturation and high voltage induction
5074. A transformer cannot raise or lower the voltage of a D.C. supply because_______________?
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A. a D.C. circuit has more losses

B. none of the above

C. Faradays laws of electromagnetic induction are not valid since the rate of change of flux is zero

D. there is no need to change the D.C. voltage

5075. Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is_________________?
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A. approximately equal to one

B. less than one

C. none of the above

D. great than one

5076. Which of the following protection is normally not provided on small distribution transformers ?
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A. Buchholz relay

B. Overfluxing protection

C. Overcurrent protection

D. All of the above

5077. Minimum voltage regulation occurs when the power factor of the load is_____________?
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A. leading

B. zero

C. unity

D. lagging

5078. Short circuit test on transformers is conducted to determine____________?
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A. core losses

B. hysteresis losses

C. eddy current losses

D. copper losses
5079. Negative voltage regulation is indicative that the load is___________?
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A. capacitive only

B. none of the above

C. inductive only

D. inductive or resistive

5080. A Transformer transforms____________?
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A. current and voltage

B. power

C. voltage

D. current

5081. A transformer can have regulation closer to zero___________?
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A. on zero power factor

B. on overload

C. on full-load

D. on leading power factor
5082. The secondary winding of which of the following transformers is always kept closed?
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A. Potential transformer

B. Step-down transformer

C. Step-up transformer

D. Current transformer
5083. Helical coils can be used on___________?
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A. low voltage side of high kVA transformers

B. high voltage side of small capacity transformers

C. high frequency transformers

D. high voltage side of high kVA rating transformers

5084. The efficiencies of transformers compared with that of electric motors of the same power are____________?
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A. much higher

B. much smaller

C. about the same

D. somewhat smaller

E. none of the above

5085. The thickness of laminations used in a transformer is usually____________?
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A. 4 mm to 5 mm

B. 14 mm to 15 mm

C. 0.4 mm to 0.5 mm

D. 25 mm to 40 mm

5086. The core used in high frequency transformer is usually___________?
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A. copper core

B. cost iron core

C. air core

D. mild steel core

5087. Noise level test in a transformer is a______________?
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A. none of the above

B. type test

C. special test

D. routine test

5088. Which of the following is not a part of transformer installation ?
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A. Exciter

B. Conservator

C. Buchholz relay

D. Breather

5089. Which of the following does not change in a transformer ?
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A. Voltage

B. All of the above

C. Current

D. Frequency
5090. The efficiency of a transformer will be maximum when_____________?
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A. hysteresis losses = eddy current losses

B. copper losses = hysteresis losses

C. eddy current losses = copper losses

D. copper losses = iron losses
5091. The hum in a transformer is mainly attributed to______________?
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A. load changes

B. magnetostriction

C. oil in the transformer

D. mechanical vibrations

5092. Power transformers are designed to have maximum efficiency at___________?
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A. 50% full load

B. nearly full load

C. 70% full load

D. no load

5093. If the supply frequency to the transformer is increased,the iron loss will__________?
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A. increase

B. not change

C. any of the above

D. decrease

5094. The value of flux involved m the e.m.f. equation of a transformer is____________?
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A. maximum value

B. average value

C. instantaneous value

D. r.m.s. value

5095. Which of the following statements regarding an idel single-phase transformer having a turn ratio of 1 : 2 and drawing a current of 10 A from 200 V A.C. supply is incorrect?
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A. Its secondary voltage is 400 V

B. Its rating is 2 kVA

C. Its secondary current is 5 A

D. It is a step-up transformer

E. Its secondary current is 20 A
5096. If a transformer is switched on to a voltage more than the rated voltage______________?
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A. its power factor will be zero

B. its power factor will remain unaffected

C. its power factor will deteriorate

D. its power factor will increase

5097. The function of breather in a transformer is___________?
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A. to cool the transformer oil

B. to arrest flow of moisture when outside air enters the transformer

C. to provide oxygen inside the tank

D. to cool the coils during reduced load

5098. Part of the transformer which is most subject to damage from overheating is_____________?
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A. copper winding

B. transformer tank

C. winding insulation

D. frame or case

E. iron core

5099. The transformer ratings are usually expressed in terms of______________?
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A. kW

B. volts

C. amperes

D. kVA
5100. Open circuit test on transformers is conducted to determine____________?
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A. core losses

B. hysteresis losses

C. copper losses

D. eddy current losses